Antiretroviral-naive subjects who have been HIV-infected for at least 6 months and who have consented to co-enroll in study BRA-0275 will enroll in the current protocol in order to initiate potent combination antiretroviral therapy (nelfinavir, efavirenz, abacavir, lamivudine). Subjects who have had prior antiretroviral experience but have not taken antiretroviral therapy for at least six months and show no evidence of resistance to the study medications may also been enrolled. The potent suppression of HIV replication which is predicted to follow initiation of therapy should be accompanied by a parallel decrease in cellular activation, and hypothetically, a decrease in or normalization of lymphocyte turnover. The companion study (BRA-0275) will evaluate the pre- and post- treatment lymphocyte turnover dynamics. Using this novel combination of potent therapies, the current study will characterize the virologic parameters of HIV suppression, the immunologic profile of CD4 recovery, and the potency and durability of the current regimen.